Nebulizers are used for various forms of respiratory therapy and the like, particularly for providing humidification of the lungs, often as a vehicle for providing medication deep in the lung passages. Such therapy is frequently used in conjunction with oxygen therapy, with the oxygen passing through a venturi in a nebulizer, drawing by aspiration liquid into the oxygen stream by that action. Simultaneously, the venturi causes a portion of the aspirated liquid to be comminuted into tiny, micronsized droplets to be passed out of the device to the patient, while the larger droplets settle back into the supply of liquid for recycling. This is, for example, as shown in U.S. Pat. No. 3,990,441.
Also, in the above patent, an immersion-type heater is shown for warming the liquid to be nebulized. This system has a disadvantage in that the heater itself enters into contact with the liquid for nebulizing. Accordingly, between uses, the heating element is desirably re-cleaned or re-sterilized to prevent cross-contamination between the patients.
Other attempts to provide effective heating of the liquid to be nebulized are illustrated in U.S. Pat. Nos. 3,859,398 and 3,864,544.
In accordance with this invention, a nebulizer is provided in which the liquid to be nebulized does not contact the heater element, but is separated from it by means of an inexpensive, disposable heat exchange shell.
Furthermore, the fluid is heated by passing through a long, tortuous path in sequential small amounts, so that the entire body of fluid does not have to be heated all at the same time. Also, adequate time is provided during passage through the tortuous path to bring the liquid to the desired temperature. Accordingly, better control of the temperature is available.
Also, in this invention, the heating element is placed in the cap of the container which provides better visibility of the solution level in the container. Likewise, the external heater isolates it from the oxygen flow path for added safety.